netdev - Re: [PATCH net-next 0/4] batch calls to fib_flush and arp

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Date:	Mon, 4 Jan 2016 17:12:08 -0800
From:	Salam Noureddine <noureddine@...sta.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jiri Pirko <jiri@...lanox.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/4] batch calls to fib_flush and arp_ifdown

On Mon, Jan 4, 2016 at 4:35 PM, Eric W. Biederman <ebiederm@...ssion.com> wrote:

> Two things would be very valuable with this patchset.
>
> Some numbers on how much your changes have improved the code in the case
> you care about.  I suspect the improvements are not subtle so this
> should not be hard.
>
> Can you please provide a justification for event_list.  Just skimming
> through it appears that event_list because a duplicate of the list of
> batched network devices that are passed to dev_close_many and friends.
> If the list is actually a duplicate it appears foolish to create it.
>
> Eric

The performance test I ran tries to unregister 1000 dummy interfaces
with 512K routes in the fib.
Without the patch I could unregister 35 interfaces per second and with
the patch it jumped to 620
interfaces per second. 512K is a lot of routes but I am assuming we
would get a good improvement
even with 100K routes in the fib.

I am using event_list to put all the net namespaces in the current
net_device batch on a list and only
call the NETDEV_UNREGISTER_BATCH on those namespaces. It would be
possible to just call the
notifier for NETDEV_DOWN/UNREGISTER_BATCH for all the devices on the
list and rely on the
needs_fib_flush flag to only call fib_flush once per namespace but it
seems like a waste to me.

Salam
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